1. Field of the Invention
This invention relates to a cut-off device for cutting off injection operations of an injection molding machine which forms two-layer molded pieces such as footwear soles. A process for terminating a first and a second injecting operation in such an injection molding machine is also disclosed.
2. Decription of the Prior Art
Devices such as, for example, DESMA Rotary Table Models 723 and 724 are known for producing two-layer directly formed soles by using a first injecting operation for forming an outsole layer and by using a subsequent second injecting operation for forming an intermediate sole layer, sometimes with a toe cap. To cut off or terminate the injection of material such as thermoplastic material into a mold cavity, two individual cut-off devices working independently of one another have been utilized. The first cut-off device for the first injecting operation includes a pressure transmission pin which acts on a switching element such as a microswitch. The inner terminal area of such prior art pressure transmission pin is placed directly in a mold cavity for the first injecting operation and is moved outwardly by the injection pressure to actuate a switch element housed in the injection mold, namely in the sole tip area beneath the mold cavity. When changing the mold, the switching element is changed automatically.
The second prior art cut-off device for the second injecting operation is placed on a machine column. It is not in direct connection with the injection mold in which another or second pressure transmission pin is arranged which reaches into the mold cavity for the second injecting operation. The second switch element must be coupled to the outer terminal area of this second pressure transmission pin by adjusting a telescopic tube. Such prior art cut-off system includes two individual cut-off devices which exhibit drawbacks during mold changes because an adjustment of the transmission components for the second switch element is necessary. Moreover, for each mold change the first switch element must be electrically connected.